1. Field of the Invention
The present invention relates to a non-contact transport apparatus capable of retaining and transporting a thin-plate-like workpiece in a non-contact state by attracting the workpiece under suction.
2. Description of the Related Art
Heretofore, for example, when a thin-plate-like workpiece such as a liquid crystal glass substrate for use in a liquid crystal display device, a semiconductor wafer, etc. is transported, a non-contact transport apparatus has been used, which is capable of floating and retaining the workpiece by use of fluid.
Such a non-contact transport apparatus, for example, as disclosed in Japanese Laid-Open Patent Publication No. 10-181879, includes a transport pad having a plurality of passages extending vertically therethrough. A pressure fluid supplied to the passages blows out from openings formed at a lower end portion of the transport pad, and the pressure fluid flows along the lower surface of the transport pad. The non-contact transport apparatus incorporating therein the transport pad is moved above and closer to the workpiece by use of a robot arm, etc. As a result, the pressure fluid flows at a high speed between the lower surface of the transport pad and the workpiece, whereby a negative pressure is generated by the Bernoulli effect, and thus the workpiece is attracted toward and retained by the transport pad under suction in a non-contact state.
Also, Japanese Laid-Open Patent Publication No. 2006-346783 discloses a non-contact transport apparatus which includes a supply pillar having a fluid supply port and a discharge pad fixed onto a lower portion of the supply pillar. The discharge pad includes a fluid discharge passage that is open along the circumferential direction. The fluid discharge passage is made up of a gap formed continuously along the circumferential direction of the discharge pad. The pressure fluid supplied from the fluid supply port flows from the fluid discharge passage along the circumferential direction of the discharge pad. As a result, a negative pressure is generated, and thus the workpiece is attracted under suction.
In general, such non-contact transport apparatuses transport a circular-disk shaped workpiece such as a semiconductor wafer, etc. In order to retain such a workpiece, the apparatuses flow a pressure fluid radially from the center of the transport pad through an opening thereof.